Question about convert number format

I hope you understand that the numeric data itself has no cultural difference, but the representation if the numbers in the form of text may have. One such difference is a decimal point, for example. If this the problem?

In this case, you only need to read data in some specific culture.

You can change the culture of a current thread before your text reader reads and parses the data:

System.Globalization.CultureInfo savedCulture = System.Threading.Thread.CurrentThread.CurrentCulture;
try {
   //the culture of Greek (Greece):
   System.Globalization.CultureInfo culture = new System.Globalization.CultureInfo("el-GR");
   System.Threading.Thread.CurrentThread.CurrentCulture = culture;
   //read and parse data in a usual way
} finally {
   System.Threading.Thread.CurrentThread.CurrentCulture = savedCulture;
}

Essentially, all that makes a difference while parsing a text into a numeric data; so, on a detail level, you can do

// use the culture defined above as System.IFormatProvider
// as System.Globalization.CultureInfo implements System.IFormatProvider
double value = double.Parse(someText, culture); //will throw exception in the case of invalid format
// or
if (!double.TryParse(someText, out value)) { /* ... */ } //without throwing exception
// here, we assume someText representing a single number 

—SA